Wed Mar 17 2010

Control installation

Although it's not a very impressive photo, I reinstalled all the nutplates on the F-704 bulkhead. It actually took a couple hours to install these due to the awkward angle and limited access. Some could be squeezed, but some needed bucked and I suck at riveting solo. They're good enough.

Next, I decided to get the control column mounted up. I took this photo because it clearly shows the sides of the U channel are square and parallel...

...but the the actual part was anything but square and parallel.

Curing this was easy...just tape up the jaws of the vise and do a little bending.

Much better!

First step of the installation was getting the control column mounts installed.

While I was doing that I noticed that I had never installed the bolts attaching the top and bottom most holes of the forward flanges of the seat ribs to the F-704 bulkhead. These take AN4-10A bolts. I was unsure if they were going to be long enough, but they did leave the required 1 thread showing.

...so I spent several hours and installed, torqued, and sealed all 16 of these bolts. Here's a photo through spar carry through showing all the bolts in the top and bottom bars.

Something odd about the plans though...you can see that Note 1 says it's acceptable for the rib flanges to bear on the bolt threads...

...but in the exploded view, the bolts go in from the rear, so the rib flanges don't need to bear on the threaded portion. Odd. I just installed them per the exploded view.

With that done, I temporarily positioned the control column with bolts through each mounting bearing.

You can see about 0.090 on each side of the bearing here. That's going to require one thick and one thin washer on each side.

Not sure where I learned about the dental floss trick, but it sure makes it easy to get the washers in position and install the bolt. Just pull the floss tight when positioning the column and the washers line right up.

The left side wasn't quite as straight forward. I tried guessing at it, but the first attempt put the bearings in a slight bind, so the control column didn't move completely freely. For the second attempt, I used feeler gauges to find what gap was between the control column flange and the side of the bearing.

Looks like .075.

After sorting through a bunch of washers, I found a stack that was pretty close. This is three of the thin washers stacked together.

The brass bushing which comes with the control column needed to have the ID drilled up to 0.250. I tried clamping the bushing in the vise and drilling it, but the dang drill bit kept grabbing and spinning the bushing in the vise. Since I was concerned about squashing the bushing I decided to make a clamp jig from a piece of scrap plywood. Simply a 3/8 diameter hole drilled with a cross slot...

...to allow clamping down on the bushing. Nice even clamping pressure. No way it's going to spin now.

With this rig, drilling the ID to 0.250 inch was a snap.

After making note of the gap between the ears of the U brackets at each end of the control column it was time to sand these to the correct length.

This technique works so well...just chuck the tube in a drill, spin it, and hold the end against the spinning sanding disc. The ends wind up being nice and square and it's easy to get just the right length.

Close enough!

The passenger side weldment also needed to be sanded somewhat.

Before mounting the passenger side control stick, I needed to drill the stick and socket for the quick release button. Thanks, Mike Schipper for sending me one of your extra release buttons.

A 1/4 inch hole is needed for the button to stick through.

Works like a charm.

With that complete, I installed the passenger side control stick / socket

Then did the same for the pilot side stick. Tomorrow I hope to prime and install the lower bar which will complete the four bar linkage of this control column. Until that is done these two sticks are not synchronized in the roll direction.